Esther Inglis-Arkell

These feather-like crystals are both ingested by humans for health and used by them to scrub floors and get the gunk off tiles. Take a look at what they are, and why polarized light makes them look so amazing.

The picture above is citric acid crystals, viewed through a polarization microscope. Everyone reading this has had either citric acid or scurvy sometime in their life. Citric acid, as you might imagine, is in most citrus fruits, as well as a few berries, is used by companies as a way to serve Vitamin C, and is the powder that you see on the outside of sour balls and other sour candy. The acid also dissolves a lot of grime, and thus is used in household cleaners, which is why many cleaners contain 'lemon oil.' It's a useful molecule, but who expected that it could be prettied up?

A polarization microscope shoots polarized light at objects, especially crystals. Crystals tend toward double refraction. They split beams of light which aren't polarized into two beams, travelling at right angles to each other and polarized at right angles as well. When the beams exit the crystal the two waves, which have traveled at different speeds, are out of phase with each other. A second polarization filter combine, the peaks and valleys merging together to either create huge peaks of light or dark areas, and we get the image above.

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It's not often we see the beauty in the everyday, so let us take a quick moment to appreciate the lovely thing we put in our mouths and use to clean our toilets.